I’m too lazy to translate, so just excerpt from Gorbachev blames communist hardliners & nationalists for Soviet collapse, most others blame him, but USSR was doomed from start:
Gorbachev is right to remind people of the situation when he took power in 1985. The Soviet model had reached the limits of its potential. Central state planning was incapable of responding effectively to the demands of a modern, high-tech economy. Social problems such as absenteeism, alcoholism and crime were on the rise. There was a growing sense that something had to be done.
What sunk the union was the August 1991 coup. The members of the Emergency Committee that tried to overthrow Gorbachev are thus partially responsible for the fact that Russia, Ukraine and other ex-Soviet states are now separate countries.
But while the hardliners made this possible, Yeltsin and his supporters were only too happy to exploit the opportunity. From early 1990 onwards, they played the ‘Russia card’ against the central leadership. Because Gorbachev controlled federal-level institutions, they set about capturing control of Russian institutions, demanded the transfer of power from the federal level to the Russian level and, in March 1991, issued a Declaration of Sovereignty of the Russian Federation.
This fatally undermined the union. It could tolerate the Baltic states separating, but it couldn’t survive Russia separating. Once the country’s liberals, to suit their political ambitions, decided to adopt the slogan “Russia for the Russians”, the USSR was doomed.
So, why did the USSR collapse? Because Gorbachev unleashed a process he couldn’t control and never understood. Because hardliners tried to stop him. And because liberals decided it suited their purposes to smash the union and have an independent Russia.